The present invention concerns improvements to retractable and extendable tarp cover systems for open-topped containers. The invention has particular application to vehicle-mounted containers, such as dump trucks. More particularly, the improvements relate to a tarp cover system utilizing an endless cable for extending or retracting the tarp along the length of the open-topped container.
It is well known to provide tarp cover systems for containers that utilize tarps having transversely extending bows. The bows support the tarp cover and are typically curved to accommodate heaped loads within the container body.
One such system is described in U.S. Pat. No. 5,429,408, owned by the Assignee of the present invention. In this tarp cover system, an endless cable extends along the length of the container on both sides of the container. The cover tarp includes transverse bows that terminate at bow ends, in which the bow ends are configured to slide along the endless cable. The rear-most bow end is directly connected to the cable so that as the cable is circulated between front and rear pulley systems, the cable carries the connected bow end with it. As the rear-most bow end travels along the length of the container, the tarp is gradually placed in tension and each successive bow end slides along the endless cable toward its fully deployed or retracted position. In this way, and as described in more detail in the ""408 patent, the tarp cover can be extended or retracted.
In a typical endless type cable system, such as the one disclosed in the ""408 patent, a pulley system supports the cable at opposite ends of the container body. One end of the pulley system is a driven end, and can either be manually or electrically driven. In a typical application, a hand crank is connected by way of a chain drive and sprocket to the driven pulley so that the tarp cover can be readily manually extended or retracted.
One drawback with the cable/pulley systems of the prior art is that the drive components are exposed at the front end of the container. In addition to the unsightly appearance of these components, the drive mechanisms are susceptible to fouling and deterioration, such as through rusting.
A further drawback has been that the endless cable has a tendency to stretch over time. As the cable stretches, the friction between the cable and pulleys decreases until it reaches a point at which rotation of the drive pulley can no longer circulate the cable. Moreover, if the cable stretches enough, it can become disengaged from the pulleys.
Yet another difficulty inherent in the endless cable systems is that the tarp and bows have a tendency to xe2x80x9csailxe2x80x9d or flare upward due to airflow or road vibrations. When the tarp sails, the contents within the container can spill out or can become wet in rainy conditions.
These and other detriments and difficulties with the prior art endless cable systems are addressed by the present invention. In certain aspects, the invention presents improvements to a retraction/extension system for a tarping system of the type utilizing transverse bows, traveling along endless cable assemblies on either side of the container body.
In one aspect of the invention, the tarping system includes an encapsulated drive mechanism for circulating the endless cable between pulley systems at opposite ends of the container. In the preferred embodiment, a drive axle is provided carrying drive pulleys at its opposite ends that are configured to be traversed by, and actually drive, the endless cable. A drive member is also connected to at least one end of the drive axle. The present invention contemplates a drive member of a variety of types, such as a chain and sprocket arrangement that can be either manually, mechanically, or electrically powered.
The invention contemplates encapsulating the drive axle within an elongated housing that is sized to cover most of the axle. Most preferably, the entire axle is concealed except for portions carrying the drive pulleys and drive member (such as a sprocket). The axle can be supported at the ends of the housing by a pair of bearing elements, such as a bushing or a bearing assembly.
In a further feature of the invention, the elongated housing can be provided in a fully assembled condition, with the axle, pulley and drive components all supported by the housing. The housing can then be mounted to a front panel or top rail of the container using a means for removably mounting. In one embodiment, the means for removably mounting can include a clamp assembly that includes a base clamp half and an upper clamp half. The base clamp half defines a channel for receiving at least a portion of the housing therein. The upper clamp half can be bolted onto the base clamp half to close the channel and trap the housing within the clamp.
In a preferred embodiment, the base clamp half defines holes for receiving mounting bolts therethrough. The bolts can pass through appropriately aligned bolt holes formed in the container panel or top rail and nuts can be threaded onto the ends of the bolts to mount the base clamp half onto the container. At least two clamp assemblies are mounted to the container, preferably at opposite sides. The self-contained housing and cable drive component assembly can then be positioned within the aligned base clamp halves and the corresponding upper clamp halves bolted onto the base clamp halves to fix the assembly to the container.
In another embodiment, the means for removably mounting the housing can be incorporated into the housing itself. In this embodiment, the housing includes a mounting surface that abuts the container body for mounting. The mounting surface defines a T-shaped slot along the length of the housing. Mounting bolts are provided having a head configured for non-rotating slidable movement within the T-shaped slot. With this aspect of the invention, the housing can be mounted to the container at an infinite number of locations.
In a most preferred embodiment, the elongated housing has an irregular shape, such as a D-shape. The channel in the base clamp half can be configured to accept the flat end of the D-shape, while the upper clamp half can define a curved channel corresponding to the curved portion of the D-shape. This irregular shape can prevent rotation of the housing as the drive axle rotates. In addition, the shape facilitates supporting the housing within the base clamp halves when they are mounted onto the container body, and until the upper clamp halves can be bolted down.
In another aspect of the invention, the cable drive mechanism includes an idler pulley arrangement at the drive pulley end. An idler pulley can be associated with each drive pulley on either side of the container. Preferably, the idler pulley is supported by an idler bracket mounted to the housing. In one feature, the idler pulley has a diameter that is significantly less than the diameter of the drive pulley. Moreover, the idler bracket is oriented to that the idler pulley is positioned relative to the drive pulley so the portions of the endless cable exiting each pulley is substantially parallel. This parallel orientation of the upper and lower traverses of the cable improves the driving force imparted to the tarp bows and reduces the envelope occupied by the cable drive system.
Another feature of the invention contemplates a self-adjusting rear idler pulley system that accounts for stretching of the cable over time or temporarily. With this feature, a rear idler pulley is carried by a yoke. The yoke is preferably telescopically mounted within a cylinder mounted to the container body. One end of the cylinder is closed, while the other end is open to receive the yoke in telescopic engagement. A spring is disposed between the closed end of the cylinder and the end of the yoke. In the preferred embodiment, the spring is a compression spring that exerts a force tending to push the yoke out of the cylinder. A pin mounted on the yoke extends through an elongated slot to limit the relative axial movement between the yoke and the cylinder.
In another feature of this embodiment of the invention, the pin has a diameter that is substantially less than the width of the slot in the cylinder. This dimensional difference allows the yoke to rotate to a limited extent relative to the cylinder. More particularly, this relative rotation capability can eliminate excessive load on the endless cable as the tarp cover is deployed or retracted.
Most preferably, the force generated by the compression spring can be adjusted by adjusting the height, or amount of compression, of the spring. This in accordance with a further aspect of the invention, a plunger is disposed between the closed end of the cylinder and the spring. A screw can be threaded into a cap at the closed end of the cylinder so that the screw bears against the plunger. The screw can be used to adjust the position of the plunger within the cylinder, which ultimately increases or decreases the degree of compression of the spring, and ultimately increases or decreases the amount of force applied to the yoke and idler pulley.
The invention further contemplates an anti-sail apparatus for a tarping system for an open-topped container. The tarping system includes a tarp cover supported by a plurality of bows, the opposite ends of the bows being carried by an endless cable extending along the length of the container. The anti-sail apparatus can comprise a rail attached to the container along a side rail of the container. The rail includes a ledge projecting outward from the container.
The anti-sail apparatus further includes a bracket connectable to the opposite ends of substantially all of the bows. The brackets include a portion extending downward from the bow end adjacent the ledge. In accordance with the invention, the apparatus includes a projection, such as a pin, extending from the downward portion of the bracket so that the pin is situated underneath the ledge. In other words, the ledge is disposed between the projection and the bow end so that as the bow end lifts, the projection or pin contacts the ledge of the rail to prevent further upward movement.
One object of the present invention is to improve the cable-driven tarp retraction and extension system. A further object is to do so in a somewhat modular approach to facilitate assembly of the system, particularly of the drive components of the system.
A further object is to enhance the drive capabilities of the endless cable system, most particularly by eliminating the effects of cable stretching. Still another object resides in features of the invention configured to prevent sailing of the tarp cover. These and other objects and benefits of the invention can be discerned from the following written description taken together with the accompanying figures.